Implement a trivial plugin registration to remove the dependency on the
`extensions` module. Also remove some unused code and options. Add
dependency on `requests` module (from LCG) to ensure the jira plugin
works correctly.

Former-commit-id: 2db86708

gen_klass of AlgTool: Remove obsolete usage of StoreGateSvc (done by AthAlgTool base now) (PyUtils-00-13-22)